


After-School Activities

by halcyon1993



Series: The Kinky Adventures of a Wolf and His Boy [30]
Category: Teen Wolf (TV)
Genre: 69 (Sex Position), Alpha Stiles Stilinski, Alpha/Beta/Omega Dynamics, Anal Fingering, Anal Sex, Barebacking, Body Worship, Bottom Derek Hale, Cock Slut Derek Hale, Hairy Derek Hale, Knotting, Large Cock, M/M, Mates Derek Hale/Stiles Stilinski, Mating, Mating Bites, Nipple Play, Omega Derek Hale, Oral Sex, Plot What Plot/Porn Without Plot, Riding, Rimming, Self-Lubrication, Stiles Stilinski Has a Big Dick, Teacher Derek Hale, Teacher-Student Relationship, Top Stiles Stilinski, True Mates
Language: English
Status: Completed
Published: 2018-09-06
Updated: 2018-09-06
Packaged: 2019-07-07 19:29:17
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 6,044
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/15914775
Author URL: https://archiveofourown.org/users/halcyon1993/pseuds/halcyon1993
Summary: After his dad’s job forces them to move, Stiles is sad about having to start over at a new school. But then, when he walks into his first class and finds his true mate in the gorgeous Mr. Hale, he realises that the move was really a blessing in disguise.





	After-School Activities

**Author's Note:**

  * For [Wescottwomen](https://archiveofourown.org/users/Wescottwomen/gifts).
  * Translation into Español available: [After-School Activities (Traducción)](https://archiveofourown.org/works/17912459) by [lbp98l](https://archiveofourown.org/users/lbp98l/pseuds/lbp98l)



> This is the 30th instalment in this kinky little series. Here's to 30 more! \o/

Stiles sighs as he steps out of his Jeep and onto the sidewalk outside of Beacon Hills High, the school in which he will be spending the last half of his senior year. He couldn't be less happy about it. His life is back in his hometown, all of his friends…Stiles is nobody here but the new kid, and to be the new kid is not an enviable position.

It wouldn't have been quite as bad were Stiles going to a new school at the beginning of the school year and not halfway through it, but those were the cards his dad was dealt when his boss told him last month that he was being relocated. Stiles wishes he could blame his dad for it, but it wasn't his fault and the new job came with a pay raise too good to turn down, meaning he could put more into Stiles' college fund. Stiles will just have to find a way to cope.

As he walks up the front steps to the main entrance, he can feel many pairs of eyes on him. He wishes the other teenagers around him wouldn't stare or at least had the decency not to do it so openly, but yelling at them like the alpha in him wants to would probably be a bad idea.

Eventually he manages to locate the main office and retrieve his schedule. Holding his head high, Stiles follows the directions the woman he'd spoken to gave him and soon manages to locate the classroom in which his first period will take place. He enters the room and looks cautiously around. Most of the desks are already filled, more pairs of eyes roaming over him, but Stiles barely notices.

He is too busy staring at the man writing on the blackboard.

That scent…it can't be. But it is. His English teacher is his omega.

His mate.

And he's hot as _fuck_.

The omega looks like he is somewhere in his mid-twenties. He has short black hair, long eyelashes and a beard framing his pretty yet chiselled face. His nose and lips are thin. He appears as tall as Stiles, beneath his maroon sweater it's evident that he has some considerable muscle on him and dark chest hair peeks out of the V-neck, all of which is quite unusual. Most of the omegas Stiles has ever met have been shorter than him, skinny and with minimal hair on their bodies. He hasn't given much thought to what his mate would look like before today, so he has no expectations for this man to live up to. But even if he had, even if those expectations were unrealistically high, Stiles' omega would've blown every single one of them out of the water.

He hit the fucking jackpot.

After a few more seconds of blatant staring, the man finally finishes writing on the blackboard and notices Stiles just standing there. When their eyes meet, Stiles feels like a bolt of electricity has just shot down his spine, making his breath hitch. From the way the omega's pretty hazel eyes widen, he felt it too.

The omega recovers first and clears his throat, regaining his professionalism. "Mr. Stilinski?"

"Yeah," Stiles responds, taking an involuntary step closer. He stops himself from taking another when he recalls the audience they have.

"I'm Mr. Hale. Why don't you take a seat next to Mr. Lahey for now."

Somewhat woodenly, Stiles forces himself to stop staring and walks across the classroom to the back corner, where the only empty seat in the room is located. Next to him is a tall beta with brown curls atop his head and guarded body language, but Stiles barely registers him or anything else. All he can focus on as he gets out his notebook is the velvety quality of Mr. Hale's voice and the way his black trousers hug his voluptuous ass when he turns back toward the blackboard to write something else on it with white chalk. Stiles squirms in his chair, hoping that no one around him will be able to scent the fact that he is half-hard.

It's going to be a long hour, and probably an even longer day until he can talk to Mr. Hale properly. One-to-one.

* * *

Stiles was right.

Throughout the day, his inner alpha howls in his head and scratches to get out, to get back to Mr. Hale and claim him before anyone else can get to him first. The fact that Mr. Hale is his true mate and they are literally fated to be together is obviously something his wolf doesn't understand, and the only way Stiles gets through the long hours is by forcing himself to focus on his other classes and doing some research into mating laws on his phone during lunch.

After the final bell rings, Stiles manages to wait ten minutes for the school to empty a bit before he seeks out Mr. Hale again. He finds him poring over some papers at his desk. As soon as he lays eyes on him, Stiles' inner wolf redoubles its efforts to break free of the cage Stiles has it in, a constant stream of _mine, claim, breed_ filling his head.

"I was wondering when you'd show up," the omega says without raising his head.

"Aww, did ya miss me?" Stiles asks teasingly.

Mr. Hale finishes reading whatever is on the sheets of paper and puts them in one of his drawers before finally looking up. He doesn't respond to Stiles' question but asks one of his own. "So, what are we going to do about this?"

"What d'you mean?"

"We're true mates—obviously—but as you're my student, issues could come up."

Stiles shrugs. "I don't see how."

"You don't?"

Closing the classroom door to give them more privacy, Stiles deposits his backpack on the closet student's desk and slowly walks closer, his wolf getting louder and louder with each step. "Like you said, we're true mates. I spent all of lunch looking stuff up, and us being true mates supersedes any laws about student/teacher or interpersonal relationships. No one'll be able to say anything about it, not the law, not my dad. Plus, I turned eighteen a couple months ago, so I'm not underage."

Mr. Hale's body language is torn as he likely goes through the same conundrum as Stiles, part of him wanting to give into his instincts and the other half resisting.

"That's, uh…that's good to know," the teacher says.

As Stiles keeps approaching, Mr. Hale pushes himself away from his desk. At first Stiles tenses and readies himself to pounce, thinking that the omega is going to try to initiate a chase, but when Mr. Hale doesn't go any further but just sits in his chair with his legs partially spread, Stiles makes himself relax.

"Something the matter?" the teacher enquires, the beginnings of a smirk on his lips. He knows just how much he is affecting his student.

"Yeah," Stiles replies. "My wolf's just kinda chanting _mine, mine, mine_ in my head and it's very distracting."

"We probably shouldn't do anything here, in school, in my classroom."

"No. We shouldn't," Stiles agrees.

Hazel stares into honey for several quiet seconds, and then, as if some kind of starting gun has been fired, they leap at each other at the same time, neither one seeming to care that there are still other students wandering the halls and the blinds aren't pulled down to cover the classroom windows. Their mouths meet in a messy kiss full of tongue and teeth clacking together. Stiles wraps his arms tightly around his omega, pressing them together and giving him no chance at all to escape his grasp. Mr. Hale could probably do so if he really wanted to—his muscles are big enough—but Stiles is extremely glad when the teacher does nothing of the sort. Instead, Mr. Hale kisses him back with fiery passion and winds his large arms around Stiles too, one hand cupping the back of Stiles' neck and the other resting on the small of his back.

For Stiles' part, he fists one hand in the soft hair on the back of Mr. Hale's head and with the other grabs a handful of that delectable ass that has been plaguing his thoughts since he first saw it at the start of the day. Mr. Hale whimpers into his mouth when Stiles squeezes it, and already Stiles thinks he can feel some dampness in the fabric of the omega's smart black slacks. It's his turn to moan when he realises that it's his mate's slick.

Wrenching his mouth away, Stiles pulls back and begins tearing at Mr. Hale's clothes, needing to see him naked, to get inside him and lay his claim.

"What's your name anyway?" he asks breathlessly, pulling up the hem of the omega's sweater. "Can't exactly call you 'Mr. Hale' forever. Unless you feel like getting kinky."

"D-Derek," the teacher answers, lifting his arms to allow Stiles to pull off the sweater.

Once he has thrown the offending garment into the corner, Stiles does the same thing with the white tank top beneath it and steps back to look at his omega. _God_ …Derek's body is even better than he'd been imagining all day.

"Damn, you're hot," he compliments, his cock rock-hard.

A faint blush appears on Derek's face and the tips of his ears turn red to match. "Thanks."

Stiles spends what is probably far too long just looking at his mate, but he can't help it. Derek's chest is the first thing that catches his attention. He'd already known that Derek had chest hair, but seeing all of it is something else. He wants to run his fingers through it, to feel the omega's large pecs beneath his palms and play with his dusky nipples.

So he does.

He presses both palms to Derek's pecs and ruffles the field of dark hair covering them, his pinky fingers catching on Derek's nipples. The omega inhales sharply and thrusts his chest out, his lips parted and his pretty eyes hooded. He obviously wants more, and it would take an alpha with far more self-control than Stiles to resist.

Stiles tugs lightly on Derek's chest hair and then moves to his nipples, twisting them between his index fingers and thumbs. He is gentle at first, but when all Derek does is whimper so sweetly he twists and pinches them with more force. Stiles' own nipples are sensitive and he has spent many nights playing with them while he jacks off to some porn on his MacBook, but he knows that, as an omega, the delicious blend of pain and pleasure Derek feels must be even more intense.

"Feel good?" he asks, just to make sure.

"Y-yeah…" Derek responds, his voice high and breathy.

Stiles twists the omega's nipples a couple more times before pushing him back in his desk chair, kneeling and getting his mouth on him. The taste of his mate's skin is amazing, and Stiles spends a long time between Derek legs while he nibbles and sucks on his nipples. When he eases off and instead blows cold air on one of the swollen nubs, he wonders if this is what Derek's nipples will look like when he is breastfeeding—which of course sends Stiles on a very dangerous tangent in which he can't help but picture Derek's abs being replaced by a round belly.

It's far too soon for anything like that—he is still in high school and can't see pups being on the table until he is at least done with college—but the picture is burned into his mind now and he can't get rid of it. It drives his inner alpha crazy and makes the base of his cock throb in his underwear, desperate to plug his omega up and fill him with his seed.

To breed him.

"Fuck…" he mumbles, grabbing himself over his jeans to stop his knot from forming.

Derek makes a confused noise above him. "What's wrong?"

"Nothing. Just thinking dangerous thoughts. You're, uh…you're not going into heat, right? I read that sometimes an omega meeting their true mate can bring one on and I don't have a condom."

Understanding appears on Derek's face. "No, I'm fine; you can't get me pregnant right now."

"Good." Stiles panics when he realises how that could sound. "Not that I don't want pups with you in the future!"

"Stiles?"

"Yeah?"

"Shut up. I'm gonna have to throw this chair out as it is, I'm soaking it so much. Let's not waste any more time with pointless discussions, okay?"

Stiles' brain short-circuits at this and it takes Derek snapping his fingers in his face for it to come back online. He shakes his head, stands back up and pulls the omega with him. Like Derek had said, when he looks around him at the chair, Stiles sees a substantial patch of slick has been left behind, the scent of it pungent. It makes his eyes flash red.

Fumbling with Derek's belt, Stiles swiftly gives up on undoing it and just cuts through it with a claw, much to Derek's dismay.

"Seriously?" the omega complains. "I really liked that belt…"

"I'll buy you a new one."

Now that the belt is out of the way, Stiles undoes the button and yanks down the zipper of Derek's slacks before shoving them and his underwear down. They fall easily and then Derek steps out of them and kicks off his shoes and socks, leaving him completely naked. Something about the fact that his omega is totally nude while he himself is still fully dressed drives Stiles' wolf crazy, makes him feel both possessive and protective. He glances over his shoulder at the door to double-check that there is no one looking through the small window and breathes a sigh of relief when he sees that there isn't. No one else gets to look at his omega when he is like this.

His inner alpha calming down slightly, Stiles turns his attention back to Derek and takes a step away to drink in the full sight of him.

"Damn, I wonder what I did in a past life to be lucky enough to get matched with _you_."

Derek rolls his eyes.

Stiles catalogues every part of his mate's body. Like his chest and arms, Derek's legs are hairy too. His dark pubes are wild and untamed around the base of his cock and his decorative balls hang low between his thighs.

Needing to touch him here as well, Stiles weighs the omega's balls in his palm and is surprised by how heavy they are. They are unlike any omega's balls he has heard about or seen in porn—and he has watched _a lot_ of porn. They are smaller than his own but still sizeable, and his cock…Stiles is honestly fascinated. Derek's cock is uncut, the bulbous head still concealed by wrinkled skin even though he is fully hard, and he is long and thick for an omega, totalling at approximately seven inches in length. Stiles knows from his biology class back at his old school that the average omega penis is just four inches long, but he supposes he should have expected Derek to be packing something different. After all, everything else about Derek has differed from what a typical omega is supposed to be like, so why wouldn't his genitals be like that too?

For a moment, Stiles wonders what it would feel like to bend over and take Derek's cock in his ass. Such a desire has never struck him before. He is an alpha, so he is supposed to do the fucking. He isn't supposed to want to get fucked himself. Stiles still plans on getting inside Derek today, but maybe in the future they can do some…experimenting.

"Where's your mind at?" the omega asks him.

Shaking his head again, Stiles waves away the question. "Don't worry about it. Turn around and lemme see your ass."

Derek looks like he wants to say something more, but he does as he has been told. He leans over the side of his desk, rests on his elbows and arches his back, the perfect position to thrust his ass out in Stiles' direction.

Said alpha is speechless, which is something that very rarely happens to him. Like the rest of him, Derek's ass is perfectly sculpted, two tight globes of muscle and somehow tanned skin that are dusted with yet more dark hairs. These hairs are matted down with slick around the crack, and as Stiles stares he sees a trail of the stuff run down the back of Derek's thigh, matting down the hairs there too. He only jumps into action when the omega looks back at him over his shoulder with an eyebrow raised and shakes his ass a bit to entice him.

Dropping carelessly to his knees, not even registering the pain in his kneecaps as they slam against the hard floor, Stiles squeezes Derek's ass cheeks a couple times to test their musculature and then pulls them apart to reveal the tight hairy hole in between. Slick leaks profusely from it, the sweet scent of it clogging Stiles' nostrils so that it's all he can smell. Unable to resist such a lure, he dives right in, shoving his face between Derek's hairy cheeks and licking up all the slick he can. It's warm on his tongue and slides so smoothly down his throat when he swallows it. It tastes like all of his favourite flavours combined, making him ravenous. His chest rumbles with a constant growl as he laps aggressively at his omega's clenching rim, getting more of his slick right from the source.

Derek pushes back against his face and whimpers so prettily, obviously enjoying his alpha's ministrations. By the time Stiles runs out of oxygen and has to take a break, his face is shiny with slick. It drips down his chin and lands with a splat on his T-shirt.

Licking his lips, Stiles wants to move on to the main event already and impatiently tugs at his own clothes. He yanks off his T-shirt and makes quick work of removing his shoes and the clothes on his bottom half, finally freeing his aching cock from the confines of his jeans and boxer-briefs. Once he isn't wearing a stitch of clothing, the playing field levelled, he smacks Derek once on his hairy ass and gets up.

"I have an idea," he says, looking at the surface of the desk.

Derek yelps at the spank but doesn't seem offended by it. Stiles files that away for later. "What is it?" the omega asks him.

"How valuable is all the stuff on here?"

"Uhh…not very. Why?"

Pleased, Stiles moves Derek out of the way and then sweeps his arm across the desk, brushing everything to the floor. Papers flutter in the air and a pot of pens and pencils clatters across the linoleum.

"Hey!" Derek exclaims, glaring at him.

Stiles blinks innocently. "What?"

"You could've warned me."

"I thought I did. Not my fault you didn't read between the lines."

The dominant nature of his inner alpha coming out, Stiles climbs insouciantly on top of Derek's desk and lies lengthways across it on his back. He heads off any further protests by giving his cock a stroke, drawing Derek's gaze to it.

The omega's breath hitches. "Oh…"

"Yeah."

"That's…big."

"Well yeah, I'm an alpha, dude; it's gonna be big. Now c'mon, get up here. Kneel the other way so your ass is near my face and you can suck me off while I get you prepped for me."

For a moment Stiles expects the order to be rebuffed. He wouldn't blame Derek if it was. He didn't say please and the lust he feels is causing him to act something like the typical knothead who bosses around their omega. Ordinarily he would never even dream of acting like this—omegas are their own people and deserve their own autonomy, the right to control their own lives, a lesson that was painstakingly drilled into him by his parents ever since he was old enough to understand speech—but Stiles can't help it right now. The alpha in his head is out of its cage and he can't put it back inside, can't stop it from taking over and demanding what it wants. He stares up at Derek and the part of his brain that is still filled by rational thought is glad to see that the omega seems to be slipping into his biologically dictated role too.

Derek doesn't say another word as he joins Stiles on the desk and swings his leg over him to straddle him backward, his calves on either side of Stiles' head. This is his way of rolling over and presenting his alpha with his belly, of submitting. He has never thought of himself as particularly submissive before. There have been times in his past when he let the few alphas and betas he has slept with take the reins, but it was never like this. Perhaps it's because Stiles is his true mate, his true alpha, that Derek's inner omega is reacting like this. He can't resist the plaintive whining in his head.

The fact that it's someone years younger—and his student to boot—that he is so desperate to please doesn't seem to matter at all.

Like Stiles said it would, Derek's new position puts his ass in front of Stiles' face and his own right above the alpha's cock. The salty musk of Stiles' sex is intoxicating. He startles momentarily when he feels Stiles slide a long finger into his needy hole, but he quickly gets used to the feeling and focuses on the thick length in front of him.

Stiles' cock is one of the biggest that Derek has ever seen. He doesn't watch much porn—he prefers written material over visual—but the alphas in the few videos he _has_ watched have nothing on Stiles. He muses briefly that it always seems to be the skinnier guys who have the biggest dicks before he wraps his right hand around the base and licks a long line up the shaft from root to tip. Stiles' cock totals somewhere between nine and ten inches, and it's so thick that Derek's thumb doesn't meet his fingers. The skin is so soft and smooth, a contrast to the hardness beneath, and unlike Derek's cock, Stiles' is circumcised, the fat purple head always visible. Derek is entranced as the slit pulses and a bead of pre-come runs down the side of the shaft.

Derek is encouraged to seal his lips around the head when Stiles inserts a second finger into his hole. He can feel the slickness of the alpha's tongue lapping at his rim around his fingers and moans around Stiles' cock.

It has been so long—too long—since he has had something inside of his body that isn't his own fingers or the dildo he keeps in the middle drawer of his bedside table at home. It isn't like he hasn't had the opportunity—Derek is by no means cocky, but he knows what he looks like and he gets hit on by alphas and betas all the time, even by the occasional omega—but he rarely feels inclined to accept any passes that are made at him. He forgot how good it feels if the thing slowly fucking in and out of his hole is both foreign and warm and alive.

"God, you're so tight," Stiles murmurs behind him, sounding thrilled.

"It's been a while," Derek responds.

This causes the alpha to tense up beneath him, and he worries that he has said something to upset him. It would be understandable if Stiles doesn't want to hear about Derek's past sexual encounters while in the middle of their own. But Stiles relaxes again a few seconds later and resumes fingering Derek open, adding a third and spreading them apart deep inside, loosening him.

"Never gonna be anyone else again…" Derek hears Stiles say under his breath.

"Just you," he agrees, which appeases his alpha.

"Just me."

For a couple of minutes Derek tries to suck on as much of Stiles' cock as he can. By the time that Stiles has four fingers inside of his hole, Derek has managed to take about half of the alpha's thick length in his mouth, the head just nudging into the back of his throat. He chokes at first and pulls off sputtering, but his enthusiasm isn't affected and as soon as he has recovered he tries again. This time he finds more success, taking the head into his throat without his gag reflex kicking in. The invasion still makes his eyes water and it isn't the most comfortable thing he has ever felt, but the weight of that big cock on his tongue is nice and the discomfort is worth it for the way it makes Stiles moan loudly behind him.

"Okay, that's enough," the alpha says then, withdrawing his fingers from Derek's hole. It leaves the omega feeling unbearably empty.

"S'it time?" Derek asks him, still stroking his cock.

"Yeah, gotta get inside you. Turn around."

With slightly less coordination than he usually possesses, Derek swings his leg around so that he is straddling his alpha the other way. He shuffles backward until he feels Stiles' cock slot between his hairy cheeks. "Can I ride you?"

Stiles' eyes flash red. "By all means. Bet you'll look good split open on my cock."

"Bet it'll feel good too."

"Yeah…"

Lifting himself up a bit, Derek reaches behind himself, grasps Stiles' cock and positions the head at his hole. He is still leaking enough slick that the first slide in is smooth, if not easy. Even with four fingers' worth of prep, Stiles' cock is a lot to take, and Derek has to go slowly as he eases himself down on it. He closes his eyes and tips his head back when the last inch slips inside and he is sitting on the alpha's lap, filled up to the brim.

"Damn…how do you _still_ feel so tight?" Stiles says, his voice strained.

"I'm n-not," Derek stammers, resting his hands on Stiles' smooth chest and looking down at him. "You're just that big."

The alpha, though obviously still deeply affected by Derek's grip on his cock, smirks up at him.

Derek sighs. "You're gonna be insufferable, aren't you?"

"Yup."

"Great."

"I think so. I'm a delight."

For the next minute or so, Derek stays seated on Stiles' huge cock and allows his body to get used to it. As they are true mates, it takes less time than he thought it would, and when he tentatively lifts himself up again so that several inches slip back out, he feels no pain or discomfort, only pleasure.

"You good?" Stiles asks him, tucking his hands behind his head.

"Yeah, I'm good."

"Then get to riding me, bitch."

Derek is at first shocked at the name, but when he meets Stiles' eyes he finds only playfulness in them. The alpha didn't mean anything bad by it. "Bossy."

Stiles winks. "You love it."

Saying nothing, neither to confirm nor deny it, Derek pushes himself back down and starts up a slow pace. Stiles' cock is thick enough that it slides against his prostate without him even having to angle himself properly, and his own cock leaks more and more pre-come onto the alpha's stomach every time he takes him in all the way. Soon enough, Derek's confidence grows and he increases the speed at which he rides his alpha, aiming to wipe the cocky smirk from his lips, to make his eyes roll back in his head as he loses control. One of his favourite things to do is to affix the suction cup on the bottom of his dildo to the floor of his shower and ride it for as long as his thighs can support him, so he has a lot of experience doing this, his movements practised and sure.

"You're good at this," Stiles comments, his voice shaky now. It's working.

Derek explains about his dildo and is the one smirking when Stiles bites into his bottom lip to stifle a moan.

After a while, Stiles tires of not touching his omega. Derek looks just stunning on top of him, taking his own pleasure. All of that tanned, hirsute skin beginning to glisten with a thin sheen of sweat, his muscles in stark relief as he rides him, his pecs bouncing slightly as he slams himself down on Stiles' thick cock…it all looks unbelievably good, like the hottest wet dream Stiles has ever had. Only it isn't a dream. Derek is real and alive, and the fact that Stiles will get to enjoy this omega just like this for the rest of their lives is a dizzying thought.

He removes his hands from beneath his head and rests them on Derek's thick thighs instead. The dark hairs tickle his palms and he can feel the way the muscles flex and contract as the omega continues to ride him.

"I'm getting close," Derek warns him, his cock smacking repeatedly against his hairy abs.

To help him along, Stiles wraps one hand around his cock and strokes him. At first it's slightly awkward as he struggles to find a rhythm with Derek, but he gets there and, when he rubs hard at the glans through Derek's foreskin, the omega goes off like a rocket. He showers Stiles in omega seed, the thin, nearly clear fluid splashing across Stiles' chest and hitting him in the face a couple of times. He closes his eyes just in time to avoid getting any in them.

When Derek's orgasm finishes, he stops riding Stiles and leans back on his arms, his hands on Stiles' shins.

"Can I?" Stiles asks him, desperate to come himself.

"Go ahead. I can take it. Want your knot."

He is oversensitive, but Derek doesn't complain when Stiles plants his feet on the desk and thrusts brutally up into him, purely chasing his own orgasm. He grunts every time the alpha fills him up completely and groans when he feels the beginnings of Stiles' knot tugging on his rim. It's a delicious pain, zinging up his spine and making his soft cock twitch where it rests over his drained balls.

"Nearly there," Stiles tells him, even though he already knows. "Hold on."

With one final thrust, Stiles fucks in deep and stays there as his knot engorges the rest of the way, locking them together. He all but howls, and if the other people who are still in the building hadn't heard them before, they definitely heard that. Derek flushes with premature embarrassment but doesn't put his hand over Stiles' mouth to quiet him. He likes knowing that he is making his alpha feel good, and that howl, as well as the warmth spreading through his insides as they are painted with thick seed, is irrefutable proof.

When Stiles comes down from his high, he is tempted to go boneless atop the desk. Only the itching in his gums prevents him from doing so.

"Come here," he orders, grabbing Derek's wrist to pull him down.

Derek comes willingly, and a second later Stiles materialises his fangs and sinks them deep into the patch of skin between Derek's shoulder and neck. He tastes blood but doesn't retract his fangs until he is one hundred percent sure he has left a mark that will turn into a lifelong scar. When he is, Stiles licks a few times over the wound to soothe it and wraps his arms around Derek's sweaty back, holding him close. It's an awkward position since they're the same height, but he is content and wouldn't change a thing about it or the omega on top of him.

"You good?" he asks him.

"Perfect," Derek murmurs, his breath ruffling Stiles' hair.

Stiles chuckles. "Yeah, you are."

"Flattery will get you everywhere."

It takes half an hour for Stiles' knot to go down. Once it does, Derek clambers off of him and winces when he feels the alpha's come slipping out of his hole. He clenches it to try to stop it from escaping, both to save on cleanup and because he wants it to stay inside him, but Stiles' cock stretched him out so much that his attempts aren't as successful as he'd like. Stiles is absolutely no help. As soon as he notices Derek's little problem he laughs and puffs out his chest proudly.

"Shut up," Derek growls, feigning irritation.

"Nope," is Stiles' response. He pops the P obnoxiously.

In the end, after Stiles checks to make sure the coast is clear, Derek makes a mad dash for the toilet across the hall and cleans up as best he can in there.

Once he is done and dressed, he rejoins Stiles in his classroom. "So."

"So."

"We're mated now," Derek points out. He can feel the connection between them pulsing with life.

The smirk that Stiles still wears softens into something more affectionate. "Yup. Wanna come to dinner? We're having steaks, and you can meet my dad."

"That's not too fast?"

Stiles raises an eyebrow at him and then glances at the desk, the surface of which is still smeared with remnants of their combined come and slick.

"Fair point," Derek concedes. He takes a breath. "Sure. I'd like that."

"Get your stuff then. I'll clean this up and then we can go."

Five minutes later, Stiles takes Derek's hand and leads him outside. They pass a few people in the halls, students who have just finished with after-school activities or other teachers who have stayed late to grade papers, and the expressions on their faces makes it very clear to Derek that they all know exactly what has just transpired between him and the alpha still leading the way to the parking lot.

Derek's first instinct is to bow his head, but he pushes through it. He meets their eyes and looks at them as if to say, "And what?"

"What's your dad like?" he asks Stiles when they get outside.

"Getting cold feet?"

"No, I've just…I've never 'met the parents' before. I want to know what to expect."

"Relax," Stiles says softly, using their linked hands to draw Derek into an embrace that is far more calming than it has any right to be. All Derek can smell is the spiciness of Stiles' alpha scent, which acts like a balm to his nerves. "He'll love you."

"You're sure?"

"I mean, he'll be shocked at first, and I'm sure he'll have a million questions, but he's a pretty laid-back guy, really. Just be yourself. You'll win him over in no time."

"That your expert opinion?"

"Hey, you won me over in two seconds flat."

"That's because we're true mates."

Stiles rolls his eyes. "Whatever. Just get in your car, follow my Jeep and try to stop thinking so much, okay?" He raps his knuckles lightly over Derek's temple.

It's hard, because it's in Derek's nature to overanalyse everything, but he makes himself stop because his alpha told him to. "Okay."

"Great!"

Stiles pecks him on the lips and then walks away toward a hideous sky-blue Jeep.

Derek watches him go for a moment and then proceeds to his own car, a sleek black Camaro that was a graduation gift from his parents. After he gets in and buckles up, he sees Stiles wave at him from behind the wheel of his Jeep and can't help but smile as he inserts his key into the ignition and brings his car to life, ready to move when Stiles does. He wasn't anticipating meeting his alpha when he got up that morning, and he _definitely_ wasn't anticipating them being a student who is equal parts goofy and cocky, the antithesis of his own personality.

Even so, Derek couldn't be happier with how the day has turned out.

**Author's Note:**

> Oops, instead of writing another chapter of either of the two full-length fics that I have ongoing, I wrote more smut. I doubt any of you will mind, though. :P I'd like say thank you to Wescottwomen for giving me this prompt. I'd never written omega!Derek before and it was an experience I enjoyed very much. I hope this fill was everything you hoped it would be. :)
> 
> Stay tuned for my next PWP, in which Derek has the tables turned on him when he tries to have his way with Stiles after spying on him all throughout lacrosse practice. Versatile!Sterek.
> 
> **P.S. Don't forget to subscribe to me to be notified when my future fics go live, which will all be Sterek. And please check out my past fics if you haven't already and are interested.**


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